The insecticidal potential of plant extracts on the wild cochineal Dactylopius opuntiae (Hemiptera: Dactylopiidae)

The wild cochineal Dactylopius opuntiae (Hemiptera: Dactylopiidae) is a major insect pest of the prickly pear Opuntia ficus-indica in Morocco, causing significant damage to the crop and economic losses. Chemical control is the most common method used to manage this pest. However, due to the negative impacts associated with pesticide use, plant-based pesticides represent an alternative control strategy. The present study aims to evaluate the insecticidal potential of aqueous extracts of Ricinus communis and Nicotiana glauca on D. opuntiae under field conditions. Plant extracts at 10% (w/v) concentrations were applied solely or in combination with black soap at 2% (w/v) on the nymphs and adults of D. opuntiae. Moreover, the total soluble phenol and flavonoid content in the plant extracts was determined using the spectrophotometric method with Folin–Ciocalteu and aluminum chloride (AlCl₃), respectively. The combination of each plant extract and black soap exhibited high insecticidal activity against D. opuntiae nymphs and females with 100% mortality. Regarding the individual applications, plant extracts resulted in mortality rates of 72.27 ± 12.13% and 95.94 ± 1.73% for N. glauca and R. communis extracts, respectively, while black soap showed a mortality rate of 86.42 ± 6.52%. The total phenols show a higher content in N. glauca (62.43 ± 0.59 µg GAE/mg DE) compared to R. communis (21.49 ± 0.87 µg GAE/mg DE). Meanwhile, no significant difference was recorded for flavonoid content between the two plant extracts, with 7.17 ± 0.03 µg QE/mg DE for N. glauca and 7.02 ± 0.42 µg QE/mg DE for R. communis. The findings highlight the potential of applying aqueous plant extracts combined with black soap as an eco-friendly approach for managing D. opuntiae.

Keywords: Dactylopius opuntiae; Opuntia ficus-indica L.; plant extracts; black soap; insecticidal activity